The present invention relates to an electronic control device for use in an automobile.
An electronic control device which has an electric digital computer such as a microcomputer so as to electronically control the operations and the various displays of the automobile, usually uses the same power supply as that of the automobile. In the conventional electronic contol device of this type, a reset pulse for initializing the digital computer in the electronic control device is produced only when power is initially supplied by turning on the ignition switch.
If a starter motor is energized after the ignition switch has been turned on, however, the battery voltage greatly drops due to a current which dashes into the starter motor to a level which is lower than the voltage level required by an electronic control system, such as a digital computer, to operate without error. Such a drop in voltage cannot be compensated for even by the use of a constant-voltage circuit, and the electronic control system often operates erroneously. Further, sensors attached to the external side of the electronic control device often produce abnormal signals with a great decrease in the battery voltage, and this gives rise to the occurrence of erroneous operation in the electronic control system. The latter problem could not be solved even if attempts were made to make the power-supply voltage applied to the electronic control system completely constant. In other words, the latter problem could not be solved by the conventional art.